The Lion Guard are a team of animals who's duty is to protect the Pride Lands and the Circle of Life; currently led by Kion and formerly led by the late Scar. Their meeting place is the Lair of the Lion Guard.
The Lion Guard is a group tasked with the job of defending the Pride Lands from danger, and is traditionally led by the second born child of the Lion King. The leader is bestowed with the Roar of the Elders, which helps them in battle.
The first Lion Guard were led by a lion named Askari, the second born son of one of the previous Lion Kings, Askari and his Lion Guard were also responsible for forging peace between lions and elephants in the Pride Lands.
Each member of the Lion Guard has a title, depending on their personalities, physical or mystical attributes; The leader is always the fiercest while the other members are the bravest, fastest, strongest and keenest of sight. All members are bestowed a marking upon their shoulder in the shape of a lion's head. Prior to Kion's Lion Guard, previous Lion Guards consisted of only lions.
Scar led the Lion Guard before Kion, but he allowed the power of the roar to go to his head, causing him to become irresponsible with his duties and abusive of his powers. He then decided to overthrow his older brother, Mufasa and take his place as the ruler of the Pride Lands. He wanted his Lion Guard to help him, but they refused. In rage, Scar murdered them with the roar, but by using the power for evil, he lost it completely.
Many years later, Kion, the second born child of Simba and Nala and Scar's great-nephew, inherits the power of the Roar of the Elders and he becomes the new leader of the new Lion Guard. Kion recruits his friends, Bunga, Ono, Beshte and Fuli, to be part of the new Lion Guard despite the fact they are not lions.
After being informed by Kiara, Simba confronts his son and scolds him for his decision (incorrectly) believing that he wasn't taking his new responsibility seriously. Eventually, after Kion and his friends defeat Janja, Simba decides to accept Kion's decision and warmly welcomes the new Lion Guard.